rubidium

American  

[roo-bid-ee-uhm] / ruˈbɪd i əm /

noun

Chemistry.

1. a silver-white, metallic, active element resembling potassium, used in photoelectric cells and radio vacuum tubes. Rb; 85.47; 37; 1.53 at 20°C.

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rubidium British  

/ ruːˈbɪdɪəm /

noun

1. a soft highly reactive radioactive element of the alkali metal group; the 16th most abundant element in the earth's crust (310 parts per million), occurring principally in pollucite, carnallite, and lepidolite. It is used in electronic valves, photocells, and special glass. Symbol: Rb; atomic no: 37; atomic wt: 85.4678; half-life of ⁸⁷ Rb: 5 × 10 ¹¹ years; valency: 1, 2, 3, or 4; relative density: 1.532 (solid), 1.475 (liquid); melting pt: 39.48°C; boiling pt: 688°C

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rubidium Scientific  

/ ro̅o̅-bĭd′ē-əm /

1. A soft, silvery-white metallic element of the alkali group. It ignites spontaneously in air and reacts violently with water. Rubidium is used in photoelectric cells, in making vacuum tubes, and in radiometric dating. Atomic number 37; atomic weight 85.47; melting point 38.89°C; boiling point 688°C; specific gravity (solid) 1.532; valence 1, 2, 3, 4.

2. See Periodic Table

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Other Word Forms

• rubidic
  adjective

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Etymology

Origin of rubidium

1860–65; < New Latin, equivalent to Latin rūbid ( us ) red (in allusion to the two red lines in its spectrum) + -ium -ium

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Example Sentences

See Examples For:

rubidium

Our experiment used photons – quantum particles of light – and the against-the-odds journey they must undertake to pass straight through a cloud of rubidium atoms.

From Science Daily ● Aug. 4, 2026

Ionic MT said it discovered high grades of 16 different types of minerals, everything from lithium to alumina, germanium, rubidium, cesium, vanadium and niobium at the site in Utah’s Silicon Ridge.

From The Wall Street Journal ● Dec. 11, 2025

Because a vanadium peroxide molecule is negatively charged, it needed alkali cations for charge balance, Nyman said, and the researchers used potassium, rubidium and cesium alkali cations for this study.

From Science Daily ● Feb. 12, 2024

A new economic assessment will also be carried out to include byproducts potassium, cesium and rubidium, which were not analyzed in the original study, Clarke said.

From Reuters ● Jun. 19, 2023

Now, if you could watch inside you would see it change; it is now rubidium, now silver, now caesium.

From Master Tales of Mystery, Volume 3 by Francis J. (Francis Joseph) Reynolds

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